Apparatus and Method for Driving 2-Phase Srm

ABSTRACT

Disclosed is an apparatus and method for driving a 2-phase SRM capable of individually performing an initial driving by an initializing sensor and a normal driving by a driving sensor, and capable of controlling a rotation speed of the SRM by delaying a phase signal by a half period and then generating a pulse width modulation signal based on the period. The apparatus comprises: a driving sensor which detects a position of a rotor thus to generate a driving sensor signal based on a result of the detection; a microprocessor which generates a 1-phase signal and a 2-phase signal based on a rising time and a falling time of the driving sensor signal at the time of a normal driving; an oscillator which generates first and second pulse width modulation signals delayed by a preset time; and a multiplying unit which multiplies the 1-phase and 2-phase signals with the first and second pulse width modulation signals, and generates 1-phase and 2-phase driving signals based on a result of the multiplication.

TECHNICAL FIELD

The present invention relates to a 2-phase SRM (switched reluctancemotor), and more particularly, to an apparatus and method for driving a2-phase SRM by individually using an initializing sensor for an initialdriving and a driving sensor for a normal driving.

BACKGROUND ART

In the conventional method for driving a 2-phase SRM, two positionsensors are used to detect each position of a rotor, and generatedsensor signals serve to initialize and drive each phase.

FIG. 1 is a view schematically showing a construction for detecting asensor signal of a 2-phase SRM.

As shown, the 2-phase SRM comprises a 4-pole stator 10, a 2-phase rotor11, a rotor shaft 12 connected to the center of the rotor 11 fortransmitting a rotary motion of the rotor, a 2-phase shutter 13rotatably connected to the rotor shaft 12, 1-phase and 2-phase sensors14 a and 14 b for detecting a position of the shutter 13, and a sensorsignal generator 15 for generating 1-phase and 2-phase sensor signalsfrom signals detected by the 1-phase and 2-phase sensors 14 a and 14 b.

Each phase of the shutter 13 has an angle of 120°, and the two phasesform an angle of 60° therebetween.

The 1-phase and 2-phase sensors 14 a and 14 b form an angle of 90°therebetween, and are positioned on the shutter 13.

In the conventional method for driving an SRM, when the shutter 13 isrotated as the rotor 11 is rotated, the sensors 14 a and 14 b detecteach position of each phase of the shutter 13. Then, the sensors 14 aand 14 b transmit the detected position to the sensor signal generator15 thus to enable 1-phase and 2-phase sensor signals to be generated.

That is, the 1-phase and 2-phase sensors respectively detect eachposition of each phase of the rotor, and then a microprocessor (notshown) generates 1-phase and 2-phase signals corresponding to the sensorsignals. Accordingly, a current is supplied to each winding of eachphase of the SRM thus to generate a torque.

FIGS. 2 to 5 show sensor signals according to each position of a rotorof the 2-phase SRM in accordance with the conventional art.

As shown, when the rotor 11 is counterclockwise rotated, the shutter 13connected to the rotor shaft 12 starts to be rotated. The 1-phase and2-phase sensors 14 a and 14 b detect a position of the shutter 13 thusto detect a position of the rotor 11. Accordingly, the sensor signalgenerator 15 generates a sensor signal of each phase.

Referring to FIGS. 2 to 5, when the rotor 11 is aligned, the shutter 13is positioned at an angle of 0°.

FIG. 2 shows a high 1-phase sensor signal S1 and a high 2-phase sensorsignal S2 when the shutter 13 is positioned within a range of 0°˜30°.

FIG. 3 shows a high 1-phase sensor signal S1 and a low 2-phase sensorsignal S2 when the shutter 13 is positioned within a range of 30°˜90°.

FIG. 4 shows a high 1-phase sensor signal S1 and a high 2-phase sensorsignal S2 when the shutter 13 is positioned within a range of 90°˜120°.

FIG. 5 shows a low 1-phase sensor signal S1 and a high 2-phase sensorsignal S2 when the shutter 13 is positioned within a range of 120°˜180°.

A microprocessor (not shown) generates each sensor signal of each phaseand modulates each pulse width of the generated signals, thereby drivingthe SRM.

FIG. 6 is a curve showing an SRM driving torque in accordance with theconventional art.

As shown, a 1-phase signal having a dwell time of 0°˜120° and 180°˜360°of one cycle of 360°, and a 2-phase signal having a delay of 90° fromthe 1-phase signal are modulated from the first and second sensorsignals shown in FIGS. 2A to 2D thus to be inputted to each winding ofthe 2-phase SRM. Accordingly, a torque is generated as indicated by thecurve of FIG. 3.

However, the conventional art has the following problems. Since the1-phase sensor initializes and normally-drives a 1-phase and the 2-phasesensor initializes and normally-drives a 2-phase, a sufficient amount ofcurrents are not supplied to each winding of each phase of the SRM atthe time of an initial torque occurrence in a normal driving mode (e.g.,t1, t2 and t3 of FIG. 3). Accordingly, a torque is not sufficientlygenerated thus not to normally drive the SRM.

That is, when the 2-phase SRM is driven at a high speed, each phasesignal has to be risen at a point prior to an initial point so as togenerate a sufficient amount of torque. However, in the conventionalart, the 1-phase sensor and the 2-phase sensor detect sensor signals atthe same position in an initial driving mode and a normal driving mode,thereby generating each phase signal and a signal for driving the SRM.Accordingly, a sufficient amount of torque is not generated at the timeof driving the SRM at a high speed.

Furthermore, a dwell time and a rising delay time of a pulse widthmodulation signal are controlled based on a phase signal in order tocontrol a rotation speed of the SRM. However, when the SRM is driven ata high speed, the phase signal has a short period and thus themicroprocessor has a limited operation speed. Accordingly, it isdifficult to control the dwell time and the rising delay time of thepulse width modulation signal based on the phase signal having a shortperiod.

DISCLOSURE OF THE INVENTION

Therefore, it is an object of the present invention to provide anapparatus and method for driving a 2-phase SRM capable of individuallyperforming an initial driving by an initializing sensor and a normaldriving by a driving sensor, and capable of controlling a rotation speedof the SRM by delaying a phase signal by a half period and thengenerating a pulse width modulation signal based on the period.

To achieve these objects, there is provided an apparatus for driving a2-phase SRM (switched reluctance motor), comprising: an initializingsensor which detects each position of each phase of a 2-phase SRM, andgenerates an initializing sensor signal based on the detected result; adriving sensor which detects each position of each phase of the 2-phaseSRM, and generates a driving sensor signal based on the detected result;and a microprocessor which initially drives the 2-phase SRM based on theinitializing sensor signal at the time of an initial driving, andnormally drives the 2-phase SRM based on the driving sensor signal atthe time of a normal driving.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration view schematically showing a 2-phase SRM fordetecting each sensor signal;

FIGS. 2 to 5 are views showing sensor signals according to each positionof a rotor of the 2-phase SRM;

FIG. 6 is a curve showing a torque according to a driving method for the2-phase SRM in accordance with the conventional art;

FIG. 7 is a block diagram showing a configuration of an apparatus fordriving a 2-phase SRM according to the present invention;

FIG. 8 is a waveform showing each portion of the apparatus for driving a2-phase SRM at the time of an initial driving according to the presentinvention;

FIG. 9 is a waveform showing each portion of the apparatus for driving a2-phase SRM at the time of a normal driving according to the presentinvention; and

FIG. 10 is a flowchart showing a method for driving a 2-phase SRMaccording to the present invention.

MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

FIG. 7 is a block diagram showing a configuration of an apparatus fordriving a 2-phase SRM according to the present invention.

As shown, the apparatus for driving a 2-phase SRM according to thepresent invention comprises an initializing sensor 71 a, a drivingsensor 71 b, a microprocessor 72, an oscillator 73 and a multiplyingunit 74.

The initializing sensor 71 a detects a position of a rotor of the2-phase SRM at the time of an initial driving, and outputs aninitializing sensor signal based on the detected result.

The driving sensor 71 b detects a position of a rotor of the 2-phase SRMat the time of a normal driving, and outputs a driving sensor signalbased on the detected result.

The microprocessor 72 generates 1-phase and 2-phase signals from theinitializing sensor signal and the driving sensor signal outputted fromthe initializing sensor 71 a and the driving sensor 71 b.

When the 2-phase SRM has an rpm more than a preset rpm after beinginitially driven, the microprocessor 72 normally drives the 2-phase SRM.

The microprocessor 72 generates 1-phase and 2-phase signals based on theinitializing sensor signal at the time of an initial driving, andgenerates 1-phase and 2-phase signals based on the driving sensor signalat the time of a normal driving.

The 2-phase signal has a phase different of 90° from the 1-phase signal.

The oscillator 73 generates pulse width modulation signals from the1-phase and 2-phase signals generated from the microprocessor 72. Also,the multiplying unit 74 multiplies the 1-phase and 2-phase signals withthe pulse width modulation signals, thereby generating signals fordriving the SRM (an initializing signal and a driving signal).

The initializing sensor 71 a is positioned so that the initializingsensor signals can be dwelled between a mis-aligned position and analigned position of the 1-phase or 2-phase inductance profile.

The driving sensor 71 b is positioned so that the driving sensor signalcan be risen before the mis-aligned position of the 1-phase or 2-phaseinductance profile.

Preferably, the driving sensor is positioned so that the driving sensorsignal can be risen before the initializing sensor signal by 10°˜30°.

The oscillator 73 generates a single pulse width modulation signal atthe time of an initial driving, and generates first and second pulsewidth modulation signals at the time of a normal driving.

At the time of a normal mode of the SRM, each dwell time of the firstand second pulse width modulation signals can be varied according to adriving speed of the SRM, and can be risen after being delayed by apreset delay time.

The oscillator 73 generates a first pulse width modulation signaldelayed by a preset time based on a falling time of the driving sensorsignal, and generates a second pulse width modulation signal delayed bya preset time based on a rising time of the driving sensor signal.

Preferably, the preset time corresponds to a half period of the drivingsensor signal.

The multiplying unit 74 may be implemented at the microprocessor 72 in asoftware manner or in a hardware manner.

FIG. 8 is a waveform showing each portion of the apparatus for driving a2-phase SRM at the time of an initial driving according to the presentinvention.

As shown, the initializing sensor is positioned on the shutter so thatthe initializing sensor signal can have a dwell time between amis-aligned position and an aligned position of the 1-phase inductanceprofile so as to generate a maximum initializing torque.

The microprocessor generates a 1-phase signal based on the initializingsensor signal, generates a 2-phase signal having a phase difference of90° from the 1-phase signal, and generates pulse width modulation (PWM)signals based on the 1-phase signal or the 2-phase signal.

The 1-phase signal, the 2-phase signal, and the pulse width modulationsignal are multiplied with one another, thereby generating 1-phase and2-phase driving signals.

FIG. 9 is a waveform showing each portion of the apparatus for driving a2-phase SRM at the time of a normal driving according to the presentinvention.

As shown, in order to provide a sufficient amount of currents to the SRMat the time of a torque occurrence time point (a mis-aligned time pointof the 1-phase inductance profile), the driving sensor is positioned onthe shutter so that the driving sensor signals can be risen before themis-aligned position of the 1-phase inductance profile by a presetangle.

Preferably, the driving sensor signal is risen before the initializingsensor signal of FIG. 5 by 10°˜30°.

The microprocessor generates a 1-phase signal based on rising of thedriving sensor signal, and generates a 2-phase signal based on fallingof the driving sensor signal, the 2-phase signal having a phasedifference of 90° from the 1-phase signal.

Then, the microprocessor generates each phase driving signal bypulse-width modulating the 1-phase signal and the 2-phase signal. Thatis, the microprocessor generates a 1-phase driving signal by multiplying(AND-operating) the 1-phase signal based on a rising time of the drivingsensor signal with a first pulse width modulation signal generated basedon a falling time of the driving sensor signal. Also, the microprocessorgenerates a 2-phase driving signal by multiplying (AND-operating) the2-phase signal based on a falling time of the driving sensor signal witha second pulse width modulation signal generated based on a rising timeof the driving sensor signal.

Differently from each phase signal, the first and second pulse widthmodulation signals are risen based on the falling time and the risingtime of the driving sensor signal, respectively.

For instance, in case of a normal driving of the SRM having 100,000 rpm,the first and second pulse width modulation signals are risen based onthe falling time and the rising time of the driving sensor signal,respectively, so as to ensure an operation time of the microprocessorthat controls a rotation speed.

The first and second pulse width modulation signals are respectivelyrisen after being delayed by a preset time based on the failing time andthe rising time of the driving sensor signal.

The preset time may be a half period of the driving sensor signal, andpreferably is a preset rising delay time.

When the SRM is normally driven at a high speed, the 1-phase signal orthe 2-phase signal has a short period and thus the microprocessor cannot easily control a period of a pulse width modulation signal and apulse width based on the 1-phase signal or the 2-phase signal.Accordingly, the second pulse width modulation signal is risen by beingdelayed by a half period (or a rising delay time added to the halfperiod) based on the rising time point of the driving sensor signal.Also, the first pulse width modulation signal is risen by being delayedby a half period (or a rising delay time added to the half period) basedon the falling time point of the driving sensor signal.

Preferably, each dwell time of the first and second pulse widthmodulation signals can be variable.

FIG. 10 is a flowchart showing a method for driving a 2-phase SRMaccording to the present invention.

As shown, the method for driving a 2-phase SRM according to the presentinvention comprises generating 1-phase and 2-phase signals by using adriving sensor at the time of a normal driving mode (S61), generatingfirst and second pulse width modulation signals based on the 1-phase orthe 2-phase signal (S62), multiplying the 1-phase signal and the 2-phasesignal with the first and second pulse width modulation signals therebygenerating 1-phase and 2-phase driving signals (S63), and driving theSRM by the 1-phase and 2-phase driving signals (S64).

The second pulse width modulation signal is generated based on a risingtime of the 1-phase signal, and the first pulse width modulation signalis generated based on a rising time of the 2-phase signal.

An operation of the apparatus and method for driving a 2-phase SRMaccording to the present invention will be explained.

At the time of an initial driving, the initializing sensor 71 a detectsa position of a rotor thus to generate an initializing sensor signalbased on the detected result, thereby applying it to the microprocessor72.

Then, the microprocessor 72 generates 1-phase and 2-phase signals basedon the initializing sensor signal applied from the initializing sensor71 a.

Then, the oscillator 73 generates first and second pulse widthmodulation signals based on the 1-phase and 2-phase signals.

Then, the multiplying unit 74 multiplies the 1-phase and 2-phase signalsoutputted from the microprocessor 72 and the first and second pulsewidth modulation signals outputted from the oscillator 73 one another,thereby generating 1-phase and 2-phase initializing signals.

The 2-phase SRM is initially driven by the 1-phase and 2-phaseinitializing signals.

Then, the microprocessor 72 detects an rpm of the 2-phase SRM, andjudges whether the detected rpm is more than a preset rpm. If the rpm ofthe 2-phase SRM is more than the preset rpm, a position of the rotor isdetected by the driving sensor 71 b and 1-phase and 2-phase signals aregenerated based on the detected position of the rotor (S66).

Then, the oscillator 73 generates first and second pulse widthmodulation signals based on the 1-phase and 2-phase signals,respectively (S67).

The oscillator 73 generates the second pulse width modulation signalbased on the 1-phase signal, and generates the first pulse widthmodulation signal based on the 2-phase signal. That is, the oscillator73 generates the second pulse width modulation signal based on therising time of the 1-phase signal, and generates the first pulse widthmodulation signal based on the rising time of the 2-phase signal.

When the SRM is normally driven at a high speed, the 1-phase signal orthe 2-phase signal has a short period and thus the microprocessor cannot easily control a period of a pulse width modulation signal and apulse width based on the 1-phase signal or the 2-phase signal.Accordingly, the oscillator 73 rises the second pulse width modulationsignal by delaying by a half period of the driving sensor signal (or arising delay time added to the half period) based on a rising time pointof the driving sensor signal. Also, the oscillator 73 rises the firstpulse width modulation signal by delaying by a half period (or a risingdelay time added to the half period) of the driving sensor signal basedon a falling time point of the driving sensor signal.

Preferably, the oscillator 73 may vary each dwell time of the first andsecond pulse width modulation signals so as to control a rotation speedof the SRM.

Then, the multiplying unit 74 multiplies the 1-phase and 2-phase signalsoutputted from the microprocessor 72 and the first and second pulsewidth modulation signals outputted from the oscillator 73 one another,thereby generating 1-phase and 2-phase driving signals (S68).

The 2-phase SRM is driven by the 1-phase and 2-phase driving signals(S69).

In the present invention, 2-phase of the SRM is initially driven by theinitializing sensor at the time of an initial driving, and is normallydriven by the driving sensor at the time of a normal driving. Also, therpm of the SRM can be precisely controlled by delaying each phase signalby a half period and then generating each pulse width modulation signalbased on the delayed phase signal.

The apparatus and method for driving a 2-phase SRM of the presentinvention has the following effects.

An initial driving is performed by the initializing sensor and a normaldriving is performed by the driving sensor. Also, a rotation speed ofthe SRM is controlled by delaying a phase signal by a half period andthen generating a pulse width modulation signal based on the period.

Accordingly, a sufficient amount of torque is generated when the SRM isdriven at a high speed, and an operation time of the microprocessor isensured.

It will also be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover modifications and variationsof this invention provided they come within the scope of the appendedclaims and their equivalents.

1. An apparatus for driving a 2-phase SRM (switched reluctance motor),comprising: a driving sensor which detects a position of a rotor thus togenerate a driving sensor signal based on a result of the detection; amicroprocessor which generates a 1-phase signal and a 2-phase signalbased on a rising time and a falling time of the driving sensor signalat the time of a normal driving; an oscillator which generates first andsecond pulse width modulation signals delayed by a preset time; and amultiplying unit which multiplies the 1-phase and 2-phase signals withthe first and second pulse width modulation signals, and generates1-phase and 2-phase driving signals based on a result of themultiplication.
 2. The apparatus of claim 1, wherein the oscillatorgenerates a first pulse width modulation signal delayed by a preset timebased on a falling time of the driving sensor signal.
 3. The apparatusof claim 1, wherein the oscillator generates a second pulse widthmodulation signal delayed by a preset time based on a falling time ofthe driving sensor signal.
 4. The apparatus of claim 1, wherein theoscillator generates the second pulse width modulation signal based on arising time of the 1-phase signal.
 5. The apparatus of claim 1, whereinthe oscillator generates the first pulse width modulation signal basedon a rising time of the 2-phase signal.
 6. The apparatus of claim 2,wherein the preset time corresponds to a half period of the drivingsensor signal.
 7. A method for driving a 2-phase SRM by using aninitializing sensor at the time of an initial driving and a drivingsensor at the time of a normal driving, comprising: detecting eachposition of each phase by the driving sensor thereby generating adriving sensor signal based on the detected result at the time of thenormal driving; and driving the 2-phase SRM by delaying by a preset timebased on the driving sensor signal generated by the driving sensor. 8.The method of claim 7, wherein the driving the 2-phase SRM comprises:generating a 1-phase signal based on a rising time and a falling time ofthe driving sensor signal; generating a first pulse width modulationsignal delayed by a preset time based on a falling time of the drivingsensor signal; and generating a 1-phase driving signal based on the1-phase signal and the first pulse width modulation signal.
 9. Themethod of claim 7, wherein the driving the 2-phase SRM comprises:generating a 2-phase signal based on a rising time or a falling time ofthe driving sensor signal; generating a second pulse width modulationsignal delayed by a preset time based on a falling time of the drivingsensor signal; and generating a 2-phase driving signal based on the2-phase signal and the second pulse width modulation signal.
 10. Themethod of claim 7, wherein the preset time corresponds to a half periodof the driving sensor signal.
 11. A method for driving a 2-phase SRM,comprising: detecting each position of each phase by a driving sensorthereby generating a driving sensor signal based on the detected resultat the time of a normal driving; generating 1-phase and 2-phase signalsbased on a rising time or a falling time of the driving sensor signalgenerated by the driving sensor; generating a first pulse widthmodulation signal delayed by a preset time based on a falling time ofthe driving sensor signal, and generating a second pulse widthmodulation signal delayed by a preset time based on a rising time of thedriving sensor signal; and modulating a pulse width of the 1-phasesignal based on the first pulse width modulation signal, a modulating apulse width of the 2-phase signal based on the second pulse widthmodulation signal, and thereby generating 1-phase and 2-phase drivingsignals.
 12. The method of claim 11, wherein the preset time correspondsto a half period of the driving sensor signal.
 13. The apparatus ofclaim 3, wherein the preset time corresponds to a half period of thedriving sensor signal.